A comparative study of monoclonal gammopathies and immunoglobulin levels in Japanese and United States elderly

Occupational Exposure and Multiple Myeloma Risk: An Updated Review of Meta-Analyses

The precise etiology of multiple myeloma remains elusive, but both genetic and environmental factors have been suggested to contribute to disease risk. Several occupational categories and toxic agents have been implicated as potentially causative, yet findings from the literature are inconsistent. The aim of this review was to summarize and critically comment on the accumulated epidemiological evidence, across published meta-analyses, about the association between occupational exposure and risk of multiple myeloma. Overall, results from eleven meta-epidemiological studies underscore a significantly increased risk for firefighters, hairdressers, and employees exposed to engine exhaust, whereas farming and methylene chloride exposure have been non-significantly correlated with the disease. Further epidemiological studies are of utmost importance whilst emphasis should be placed on occupational hazard surveillance, as such studies will obtain a more accurate picture of disease occurrence in working populations, and will enable both the implementation of preventive actions and the evaluation of their effectiveness.

Determinants of Serum Immunoglobulin Levels: A Systematic Review and Meta-Analysis

Background

An up-to-date overview of determinants of serum immunoglobulins in adults is pivotal for clinical practice and research, but currently lacking. We therefore performed a systematic review and meta-analysis to identify determinants of serum immunoglobulin levels.

Methods

Embase, Web of Science, Medline, Cochrane, and Google Scholar were searched from inception to July 11^th, 2019 for articles reporting on determinants of serum immunoglobulin A, G or M (IgA, IgG or IgM) in adult humans. Random and fixed effect models were applied to obtain pooled mean differences (MDs) and 95% confidence intervals (CIs) for the association of age and sex with serum immunoglobulins.

Results

We retrieved 117 articles reporting on determinants of serum immunoglobulins, of which 28 could be meta-analyzed. Older compared to younger individuals had higher IgA (MD: 0.38; CI: 0.18 - 0.58), but lower IgM levels (MD: -0.40; 95%: -0.66 - -0.14). Men had higher IgA (MD: 0.22; CI: 0.03 - 0.42), but lower IgM levels (MD: -0.21; CI: -0.32 - -0.10) than women. Age and sex did not influence IgG. Caucasian ethnicity was associated with lower IgA, IgG, and IgM. Smoking and corticosteroid use were associated with lower IgG. Positive associations were reported of probiotics with IgG, alcohol with IgA, hypertension with IgA and IgG, and acute psychological stress with IgA, IgG, and IgM.

Conclusions

Older age and male sex are associated with higher IgA, but lower IgM, and urge investigation of age- and sex-specific reference ranges of immunoglobulins. Other identified determinants were ethnicity, diet, lifestyle and cardio-metabolic factors.

Parental longevity and survival among patients with multiple myeloma and monoclonal gammopathy of undetermined significance: a population-based study

Parental longevity is associated with an increased life expectancy; results with regard to specific diseases are conflicting. There are limited data focusing on host characteristics and their effect on survival among multiple myeloma (MM) patients and individuals with monoclonal gammopathy of undetermined significance (MGUS). Therefore, our aim was to evaluate the impact of parental longevity on survival of patients with MM and MGUS. A total of 4675 patients with MM, 6812 MGUS patients and 13 398 population-based controls for MM as well as 19 110 controls for MGUS, from 1988 to 2013, were included in the study. Longevity was defined as >90 years of age. Among MM patients, parental longevity was associated with a decreased risk of death [hazard ratio (HR) = 0·92, 95% confidence interval (CI) 0·84-0·99] and the same was true for MGUS patients (HR = 0·87, 95% CI 0·78-0·96). Having one long lived parent significantly decreased the risk of death in both groups, but was not statistically significant when both parents exceeded 90 years of age. In conclusion, parental longevity decreases the risk of death for patients with MM and MGUS which may reflect the importance of the host's genetic and environmental factors in relation to survival.

Does my patient with a serum monoclonal spike have multiple myeloma?

A monoclonal spike on serum protein electrophoresis is a frequent finding in the general population and pathognomonic of a plasma cell dyscrasia. In otherwise healthy individuals, it is diagnostic of two asymptomatic, premalignant conditions called monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) which carry a lifelong risk of progression to multiple myeloma (MM) or related malignancy. This article discusses the criteria for diagnosis of MGUS, SMM, and MM; current recommendations for follow-up and risk factors for progression to MM of patients with MGUS and SMM; and diagnostic evaluation of suspected MM transformation.

Prevalence, clinical aspects, and natural history of IgM MGUS

BACKGROUND

Waldenström macroglobulinemia (WM) and chronic lymphocytic leukemia (CLL) are related B-cell cancers that share several clinical and biological features. Both WM and CLL have associated precursor conditions: monoclonal gammopathy of undetermined significance (MGUS) of immunoglobulin M (IgM) type and monoclonal B-cell lymphocytosis (MBL), respectively. Recently, a case of MBL with an IgM MGUS was reported, suggesting a close biological relationship between these entities. While much is known about MGUS overall, investigations of IgM MGUS specifically have been fragmentary.

METHODS

In this article, we review data on the prevalence, clinical aspects and natural history of IgM MGUS, and focus on identifying gaps in our understanding of the complex relationships among B-cell malignancies and their precursors.

RESULTS

There appears to be marked heterogeneity in the prevalence of IgM MGUS across populations. However, studies have varied in definition, design, laboratory methods, and endpoints. IgM MGUS differs from non-IgM MGUS in certain respects, including prevalence across racial groups, rate of progression, and pattern of malignant outcomes. There are limited data regarding the coincident occurrence of IgM MGUS and MBL.

CONCLUSIONS

Future studies incorporating both protein electrophoresis and flow cytometry are needed to define the underlying spectrum and causes of precursor development, risk factors for progression, and markers that distinguish low- and high-risk precursor patients.

Molecular and biologic markers of progression in monoclonal gammopathy of undetermined significance to multiple myeloma

Multiple myeloma (MM) is a malignant plasma cell dyscrasia localized in the bone marrow. Recent studies have shown that MM is preceded in virtually all cases by a premalignant state called monoclonal gammopathy of undetermined significance (MGUS). This review focuses on non-IgM MGUS and its progression to MM. Although certain clinical markers of MGUS progression have been identified, it currently is not possible to accurately determine individual risk of progression. This review focuses on the various biologic and molecular markers that could be used to determine the risk of MM progression. A better understanding of the pathogenesis will allow us to define the biological high-risk precursor disease and, ultimately, to develop early intervention strategies designed to delay and prevent full-blown MM.

Prevalence of monoclonal gammopathy of undetermined significance: a systematic review

Monoclonal gammopathy of undetermined significance (MGUS) is a premalignant plasma cell disorder that is associated with a lifelong risk of multiple myeloma. We conducted a systematic review of all studies investigating the prevalence and incidence of MGUS in the online database PubMed. The review was conducted from January 6, 2009, through January 15, 2010. The following MeSH search headings were used: monoclonal gammopathy, benign and prevalence; monoclonal gammopathy, benign and incidence; paraproteinemia and prevalence; and paraproteinemia and incidence. Articles were limited to those written in English and published by January 2009. Fourteen studies that met prespecified criteria were included and systematically assessed to identify the most accurate prevalence estimates of MGUS based on age, sex, and race. On the basis of our systematic review, we estimate that the crude prevalence of MGUS in those older than 50 years is 3.2% in a predominantly white population. Studies in white and Japanese populations demonstrate a clear increase in prevalence with age. The prevalence is also affected by sex: 3.7% and 2.9% in white men and women, respectively; and 2.8% and 1.6% in Japanese men and women, respectively. Additionally, MGUS is significantly more prevalent in black people (5.9%-8.4%) than in white people (3.0%-3.6%). We conclude that MGUS is a common premalignant plasma cell disorder in the general population of those older than 50 years. The prevalence increases with age and is affected by race, sex, family history, immunosuppression, and pesticide exposure. These results are important for counseling, clinical care, and the design of clinical studies in high-risk populations.

Impact of optimal follow-up of monoclonal gammopathy of undetermined significance on early diagnosis and prevention of myeloma-related complications

Monoclonal gammopathy of undetermined significance (MGUS) is associated with a long-term risk of progression to multiple myeloma (MM) or related malignancy. To prevent serious myeloma-related complications, lifelong annual follow-up has been recommended, but its value is unknown. We reviewed all patients from southeastern Minnesota seen at Mayo Clinic between 1973 and 2004 with MGUS who subsequently progressed to MM. Of 116 patients, 69% had optimal follow-up of MGUS. Among these, abnormalities on serial follow-up laboratory testing led to the diagnosis of MM in 16%, whereas MM was diagnosed only after serious MM-related complications in 45%. In the remaining, workup of less serious symptoms (25%), incidental finding during workup of unrelated medical conditions (11%), and unknown (3%) were the mechanisms leading to MM diagnosis. High-risk MGUS patients (≥ 1.5 g/dL and/or non-IgG MGUS) were more likely to be optimally followed (81% vs 64%), and be diagnosed with MM secondary to serial follow-up testing (21% vs 7%). This retrospective study suggests that routine annual follow-up of MGUS may not be required in low-risk MGUS. Future studies are needed to replicate and expand our findings and to determine the optimal frequency of monitoring in higher-risk MGUS patients.

Monoclonal gammopathy in a tertiary referral hospital

OBJECTIVE

Monoclonal gammopathies reflect conditions of plasma B-cell disorders. Our objective was to identify the prevalence and types of these gammopathies in our population.

METHODS

A 10year retrospective study was conducted. Serum and/or urine protein electrophoresis were performed on 6624 samples. Positive bands were further tested by immunofixation (IFE).

RESULTS

Homogenous bands were detected in 7% of the patients. IFE method confirmed 6.3% in which 59% were males and 41% were females. The mean age was 64.7 for females and 66.5 for males. The sensitivity and specificity were 91% and 99% respectively. The most common protein was IgG kappa 41%, followed by IgG lambda 19%. Sixty-eight percent of these patients had monoclonal gammopathy of undetermined significance and 14.6% had multiple myeloma.

CONCLUSION

The majority of the studied population had MGUS. This observation is in concord with other western populations. The sensitivity and specificity of protein electrophoresis is diagnostically and reasonably acceptable.

Prevalence of monoclonal gammopathy of undetermined significance: study of 52,802 persons in Nagasaki City, Japan

OBJECTIVE

To assess the prevalence of monoclonal gammopathy of undetermined significance (MGUS) in a large Japanese population.

PARTICIPANTS AND METHODS

From October 1, 1988, to March 31, 2004, a total of 52,802 (of 71,675) Japanese survivors of the atomic bomb explosion in Nagasaki City, Japan, were screened for M protein. The youngest participant was 42.3 years as of October 1, 1988. A 2-step screening was performed with a serum protein electrophoresis followed by immunoelectrophoresis and a quantitative determination of serum concentration of immunoglobulins. Twenty-one patients who were diagnosed for the first time at the time of screening as having multiple myeloma and Waldenström macroglobulinemia were excluded from analyses. Age- and sex-specific prevalence rates of MGUS were calculated.

RESULTS

Monoclonal gammopathy of undetermined significance was identified in 1088 of the 52,781 study participants. The overall prevalence of MGUS was 2.1% (95% confidence interval [CI], 1.9%-2.2%) in the total population screened and 2.4% (95% CI, 2.0%-2.6%) in those 50 years or older. The prevalence was significantly higher in men than in women (2.8% vs 1.6%; age-adjusted odds ratio, 2.0; 95% CI, 1.8-2.3; P less than .001). In both sexes, the prevalence rose with increasing age from 1.0% in participants aged 42 to 49 years, 1.9% in those 50 to 59 years, 2.6% in those 60 to 69 years, and 3.0% in those 70 to 79 years, to 4.4% in those 80 years and older. The heavy chain isotypes of immunoglobulin were IgG in 73.6% of patients, IgA in 17.7%, IgM in 7.5%, and oligoclonal gammopathies in 1.1%.

CONCLUSION

The prevalence of MGUS is lower in this Japanese population than that reported in Western countries among people older than 60 years, especially among women.

Retrospective study of monoclonal gammopathies detected in the clinical laboratory of a Spanish healthcare district: 14-year series

BACKGROUND

We studied the incidence, classification and isotype distribution of monoclonal gammopathies and M-protein detected between 1992 and 2005 inclusive in the clinical laboratory of a healthcare district in Madrid (Spain) with an average population of 280,574 inhabitants.

METHODS

Serum electrophoresis was carried out on a cellulose acetate support up until 1997, and then using capillary zone electrophoresis systems, with M-protein identification carried out by agarose gel immunofixation. The age-adjusted incidences were standardized with respect to the WHO World Standard Population Distribution, based on the world average population between 2000 and 2025. The clinical diagnosis was recorded from the patient case history.

RESULTS

M-protein was detected in a total of 537 patients; of these, 42 had been diagnosed before 1992, representing a 0.19% prevalence in our population. The mean age-adjusted incidence of monoclonal gammopathy was 10.72 per 100,000 inhabitants/year (SE 1.31), ranging from 4.85/100,000 in 1992 to 14.28/100,000 in 2003 and 2004. The median patient age at diagnosis was 73 years (range 25-96 years), with males accounting for 46.8% of all cases of monoclonal gammopathy, and 57.8% of all malignant monoclonal gammopathies. A total of 54.1% of the patients were clinically defined as presenting monoclonal gammopathy of undetermined significance, 31.3% presented multiple myeloma, and the remaining 14.6% presented malignant gammopathies. The most frequent M-protein isotype was IgG (55.8%), followed by IgA (20.8%) and IgM (13.6%). A total of 88% of the light chain M-proteins, 54% of isotype IgM, 51% of isotype IgA and 36% of isotype IgG were associated with B lymphoproliferative diseases.

CONCLUSIONS

We conclude that the clinical laboratory should play an important role in the study of monoclonal gammopathies, since it is the only location where all M-protein patients are observed. On the other hand, studies of this type should be carried out over long-term periods, owing to the variations we have noted in the detection of M-proteins.

Monoclonal Gammopathy of Undetermined Significance

Monoclonal gammopathy of undetermined significance (MGUS) is characterized by the presence of a monoclonal protein (M-protein) without evidence of multiple myeloma (MM), Waldenstrom's macroglobulinemia (WM), amyloidosis (AL), or a related plasma cell proliferative disorder. Agarose gel electrophoresis followed by immunofixation is recommended for recognition of an M-protein. Monoclonal gammopathy of undetermined significance is found in approximately 3% of persons > 70 years of age and in about 1% of those > 50 years old. In a series of 1384 patients from Southeastern Minnesota in whom MGUS was diagnosed at Mayo Clinic from 1960 through 1994, the risk of progression was 1% per year. This risk of progression continued even after > or = 25 years of a stable M-protein. The risk for developing MM, WM, or AL was increased 25-fold, 46-fold, and 8.4-fold, respectively. The concentration of the serum M-protein, abnormal serum free light-chain ratio, and the presence an immunoglobulin (Ig)M or an IgA M-protein were risk factors for progression. The presence of a urine M-protein or the reduction of > or = 1 uninvolved immunoglobulins was not a risk factor for disease progression. Patients must be monitored for progressive disease throughout their lives. Variants of MGUS consist of IgM MGUS, biclonal gammopathies, triclonal gammopathies, idiopathic Bence Jones (light-chain) proteinuria, and IgD MGUS. Monoclonal gammopathy of undetermined significance may be associated with many disorders, including lymphoproliferative diseases, leukemia, von Willebrand's disease, connective tissue diseases, and neurologic disorders. Epidemiologic and statistical methods must be used to evaluate these associations.

Cancer in Jews: introduction and overview

This article is based upon a literature overview of cancer in Jews. It involves a comparison of variation in incidence and prevalence rates between Jews and non-Jews. However, the reader must exercise a certain amount of skepticism when considering secular changes in cancer incidence and prevalence and the public health implications of such cancer variation. Ashkenazi Jews have a lifetime CRC risk of 9--15%. This elevated CRC risk is similar to that of individuals in the "familial risk'' category, and differs strikingly from the 5-6% CRC risk for non-Ashkenazi members of general Western populations. A MedLine search tested the hypothesis that site-specific and/or all-cancer incidence and mortality rates are either higher or lower than expected in Ashkenazi Jews worldwide, when compared with reference populations. Results showed that all cancer incidence and mortality is not higher in Ashkenazi Jews when compared to North American non-Hispanic whites. Indeed, rates for some cancers, such as carcinoma of the lung in Ashkenazi males, are low; this example is likely attributable in large part to decreased tobacco use. Carcinoma of the ovary, pancreas, stomach, and non-Hodgkin's lymphoma have a higher incidence rate in Ashkenazi. Even though BRCA1 and BRCA2 founder mutations which predispose to carcinoma of the breast and ovary appear increased in Ashkenazi breast cancer affected women, there was no evidence supporting an elevated risk of breast cancer among Ashkenazi women. Our primary concern, however, is that Ashkenazi Jews may have one of the highest lifetime CRC risks of any ethnic group in the world, a risk that diverges significantly from that of the general population; therein, it logically calls for more intensive CRC screening guidelines. We have emphasized that the reader use caution in the interpretation of statistics which portray variation in incidence and prevalence figures for cancer in any racial, ethnic, or religious group, inclusive, of course, of Jews. Clearly, more research will be required in the interest of accuracy in the understanding of these cancer variations, since they portend the need for special cancer control strategies. A lesser degree of attention can then be given to carcinoma of the penis and uterine cervix, which occur very infrequently in Jews. We urge our colleagues to continue to probe further into these statistical differences in cancer's incidence and prevalence in order to garner a better understanding of cancer's etiology and pathogenesis.

Monoclonal gammopathies of undetermined significance: a review

Monoclonal gammopathy of undetermined significance (MGUS) denotes the presence of a monoclonal protein (M-protein) in patients without evidence of multiple myeloma (MM), macroglobulinemia, amyloidosis (AL), or a related plasma cell proliferative disorder. MGUS is found in approximately 3% of persons older than 70 years and in about 1% of those older than 50 years. In a series of 1384 patients from south-eastern Minnesota in whom MGUS was diagnosed at Mayo Clinic from 1960 through 1994, the risk of progression was 1% per year. Patients were at risk of progression even after 25 years or more of a stable monoclonal gammopathy. The risk of development of MM was increased by 25-fold, the risk of macroglobulinemia was 46-fold, and the risk of primary AL was 8.4-fold when compared with a similar population (Surveillance, Epidemiology and End Results). The concentration of the serum M-protein was the major independent predictor of progression. Patients with an immunoglobulin M (IgM) or an IgA monoclonal gammopathy had a higher risk of progression than those with an IgG monoclonal gammopathy. The presence of a urine M-protein or the reduction of one or more uninvolved Igs was not a risk factor for progression. MGUS may be associated with many different disorders, including lymphoproliferative diseases, leukemia, connective tissue disorders, dermatologic diseases, and neurologic disorders.

High rate of monoclonal gammopathy among immunocompetent subjects with primary cytomegalovirus infection

Serum samples from immunocompetent adults with primary cytomegalovirus (CMV) or Epstein-Barr virus (EBV) infection and from solid-organ or bone marrow transplant recipients with primary CMV infection were examined for paraproteins. Several immunocompetent patients with CMV infection but none with EBV infection presented with an M component, which implies that the M component connects CMV infection to a risk of B cell malignancy.

Monoclonal gammopathies of undetermined significance

The term 'monoclonal gammopathy of undetermined significance' denotes the presence of a monoclonal protein in patients without evidence of multiple myeloma, macroglobulinemia, amyloidosis or related plasma cell proliferative disorders. The disorder has been found in approximately 3% of persons older than 70 years and in approximately 1% of persons older than 50 years. A population-based study included 1384 patients from south-eastern Minnesota who had the disorder diagnosed at the Mayo Clinic from 1960 through 1994. Risk of progression was about 1% per year, but patients were at risk of progression even after 25 years or more of stable monoclonal gammopathy of undetermined significance. The risk for development of multiple myeloma was increased 25-fold; the risk of macroglobulinemia, 46-fold; and the risk of primary amyloidosis, 8.4-fold. Concentration and type of monoclonal protein were the only independent predictors of progression. The presence of a urine monoclonal protein and the reduction of one or more uninvolved immunoglobulins were not risk factors for progression. Monoclonal gammopathy of undetermined significance may be associated with various disorders, including lymphoproliferative diseases, leukemia, von Willebrand disease, connective tissue diseases and neurologic disorders.

Monoclonal gammopathy in Iceland: a population-based registry and follow-up

The term monoclonal gammopathy (MG) signifies the benign or malignant clonal growth of B lymphocytes. In the present study, monoclonal gammopathy of unknown significance (MGUS) was defined as those patients with no identified haematological malignancy. A database was constructed of all 713 MG patients in Iceland between 1976 and 1997 and compared with the Icelandic Cancer Registry. The age-standardized incidence per 100 000 of MG was 10.3 for males and 8.6 for females, calculated for the whole period, rising steadily from 5.8 (men) and 4.9 (women) during the 5-year period 1976-80 to 14.7 (men) and 12.5 (women) during the last 5 year period. Age-standardized incidence rates were very low for subjects under 50 years of age, then increased with age from 11 and 17 per 100 000 at 50-54, to 169 and 119 per 100 000 at age 80-84, for men and women respectively. No association was detected between MG and non-haematological malignancies, neither retrospectively nor prospectively. Haematological malignancy was diagnosed in 209 (29.3%) cases before the recorded finding of MG or within the same calendar year, leaving 504 (70.7%) patients diagnosed with MGUS. Of these, 51 (10%) progressed to multiple myeloma or Waldenström's macroglobulinaemia after a mean interval of 3.8 years; mean follow-up was 7.4 years, median 6 years. The most common immunoglobulin (Ig) class was IgG (55%), followed by IgM (32%) and IgA (13%). MGUS was a highly significant risk factor for developing haematological malignancies and the risk was significantly greater for MG of the IgA class compared with either IgG or IgM.

Myeloma aetiology and epidemiology

Recently there have been substantial improvements in our understanding of the biology of myeloma. These findings have important implications for aetiological studies aimed at defining the causative factors for myeloma. Myeloma is closely related to monoclonal gammopathy of unknown significance (MGUS), which is now recognized to be very common in the older population. The epidemiology of these conditions is presented and discussed in the context of the genetic factors governing both the risk of developing MGUS or of transformation to myeloma. Biological studies support a role for aberrant class switch recombination early in the natural history of myeloma suggesting that factors in the environment may interact with this mechanism to increase myeloma risk. Case-control and cohort studies have identified several known and suspected environmental exposures. These exposures include high doses of ionizing radiation, and occupational exposure in the farming and petrochemical industries. The data supporting these associations are presented and discussed in the context of the molecular mechanisms underlying these exposures. In particular DNA damage occurring as a consequence could readily interact with the class switch recombination process to increase the risk of chromosomal translocations, oncogene deregulation and malignant transformation. A further hypothesis, which has been extensively investigated, is the role of chronic immune/antigenic stimulation and the risk of myeloma. This concept is difficult to explain in the context of our current immunological concepts. The data supporting the association and how molecular epidemiological studies using genetic variants in cytokine genes are allowing us to revisit this concept are discussed in detail.

Occurrence of serum M-protein species in Japanese patients older than 50 years based on relative mobility in cellulose acetate membrane electrophoresis

We investigated the occurrence of serum M-protein species in 2,007 Japanese patients older than 50 years of age. All sera samples were analyzed by cellulose acetate membrane electrophoresis. The relative mobility of an M-protein band was calculated by dividing the migration distance of M protein by that of albumin. M proteins were found to be present in 71 of 2,007 cases (3.5%). Men 80-89 years old showed the highest occurrence of M proteins, 11.0%. The relative mobility of M-protein bands, especially the band of the IgA-type M protein, increased as the patient's age advanced. The patients had higher levels of the IgG-type M protein than healthy Japanese subjects. We found that the occurrence of M-protein species in Japanese patients increases with their age. The IgG-type M protein was most frequently expressed among other types. The mobility of the M protein was greater in older patients probably because of aging-related changes in the carbohydrate chain of immunoglobulins composing an M-protein molecule.

Monoclonal gammopathies of undetermined significance

Monoclonal gammopathy of undetermined significance is characterized by a serum M-protein level less than 3 g/dL, fewer than 10% plasma cells in the bone marrow, and no or only small amounts of M-protein in the urine; by the absence of lytic lesions, anemia, hypercalcemia, and renal insufficiency; and most importantly, by the stability of the M-protein and by the failure of other abnormalities to develop. Monoclonal gammopathy of undetermined significance is found in approximately 3% of persons older than 70 years and in 1% of those older than 50 years. Approximately one fourth of patients develop MM, AL, WM, or a similar malignant lymphoproliferative disorder during long-term follow-up. In a series of 241 patients at the Mayo Clinic, the actuarial rate of development of serious disease was 16% at 10 years and 40% at 25 years. The median interval from recognition of the M-protein to the diagnosis of MM was 10 years (range, 2-29 years). The plasma cell labeling index and the presence of circulating plasma cells in the peripheral blood suggest active disease. There are no findings at the time of recognition of MGUS that distinguish patients who will remain stable from those in whom a malignant plasma cell proliferative disorder will develop. Therefore, one must perform serial measurements of the M-protein and periodically evaluate the clinical and laboratory features.

Racial differences in the prevalence of monoclonal gammopathy in a community-based sample of the elderly

PURPOSE

To determine if there is an increased prevalence of monoclonal gammopathy in elderly blacks compared with whites, analogous to the difference in incidence of multiple myeloma reported for the two racial groups and to confirm age and gender relationships.

PATIENTS AND METHODS

Subjects were from the Duke Established Populations for the Epidemiologic Study of the Elderly, selected on the basis of stratified random household sampling. Blacks were oversampled to allow for increased statistical precision in racial comparisons. In all, 1,732 subjects (aged > 70 years) consented to blood drawing and constitute the sample for this study. Monoclonal immunoglobulins were determined by agarose gel electrophoresis and immunofixation.

RESULTS

One hundred six subjects (6.1%) had a monoclonal gammopathy. There was a greater than twofold difference in prevalence between blacks (8.4%) and whites (3.8%) (P < 0.001); monoclonal gammopathy prevalence increased with age, and was greater in men than women. Those with monoclonal gammopathy did not differ from those without in socioeconomic status, urban/rural residence, or education. The presence of monoclonal gammopathy was not associated with any specific diseases nor with impaired functional status. There was a slight increase in serum creatinine levels and decrease in hemoglobin and albumin levels in patients with monoclonal gammopathy, but no difference in interleukin-6 (IL-6) levels. Moreover, IL-6 levels were not correlated significantly with the level of monoclonal protein.

CONCLUSION

Prevalence of monoclonal gammopathy is significantly greater among blacks than whites in a community-based sample, in approximately the same ratio that multiple myeloma has been reported in the two groups. Given the absence of correlation with environmental factors, there may be a biological racial difference in susceptibility to an early event in the carcinogenic process leading to multiple myeloma.

Monoclonal gammopathy of undetermined significance and solitary plasmacytoma. Implications for progression to overt multiple myeloma

MGUS is characterized by the presence of a serum M-protein less than 3 g/dL; fewer than 10% plasma cells in the bone marrow; no, or only small amounts of, M-protein in the urine; absence of lytic lesions, anemia, hypercalcemia, and renal insufficiency; and, most importantly, stability of the M-protein and failure of development of other abnormalities, MGUS is found in approximately 3% of persons older than 70 years and in 1% of those 50 years or older. During long-term follow-up, approximately one fourth of patients develop multiple myeloma (MM), amyloidosis, macroglobulinemia, or a similar malignant lymphoproliferative disorder. Actuarial rate of development of serious disease was 16% at 10 years, 33% at 20 years, and 40% at 25 years in our experience. The interval from recognition of the M-protein to the diagnosis of MM ranged from 2 to 29 years (median, 10 years). The size of the M-protein, hemoglobin value, percentage of bone marrow plasma cells, amount of light-chain excretion, presence of hypercalcemia or renal insufficiency, and presence of lytic bone lesions are often helpful in differentiating MGUS from MM and macroglobulinemia. The plasma cell labeling index and the presence of circulating plasma cells in the peripheral blood are indicators of active disease; however, there are no findings at the diagnosis of MGUS that reliably distinguish patients who will remain stable from those in whom a malignant condition will develop. Thus, a physician must perform serial measurements of the M-protein in the serum and periodic evaluation of the pertinent clinical and laboratory features to determine whether MM, macroglobulinemia, systemic amyloidosis, or related disorders have developed. Solitary plasmacytoma is characterized by the presence of a tumor consisting of monoclonal plasma cells identical to those in MM. In addition, skeletal roentgenograms must show no lytic lesions, a bone marrow aspirate must contain no evidence of MM, and immunoelectrophoresis or immunofixation of the serum and concentrated urine should show no M-protein. Exceptions to the presence of an M-protein occur, but therapy of the solitary lesion often results in disappearance of the M-protein. Tumoricidal irradiation (4000 to 5000 cGy) for approximately 4 weeks is the treatment of choice. Overt MM occurs in approximately 50% of patients with solitary plasmacytoma. Progression occurs in most patients within 3 years. The three patterns of failure are (1) development of MM, (2) local recurrence, and (3) development of new bone lesions in the absence of MM.

Monoclonal gammopathy of undetermined significance (MGUS)

MGUS is characterized by a serum M-protein concentration of less than 30 milligrams (3 g/dl), fewer than 10% plasma cells in the bone marrow, no or only small amounts of M-protein (Bence Jones protein) in the urine, the absence of lytic lesions, anaemia, hypercalcaemia and renal insufficiency, and most importantly, stability of the M-protein and failure of the development of additional abnormalities. Electrophoresis on agarose, followed by immunoelectrophoresis or immunofixation for the identification of the type of M-protein, is recommended. In 1994, 971 patients at the Mayo Clinic were found with a serum M-protein. The most frequent diagnosis was MGUS, which occurred in 52% of patients. MGUS is found in approximately 3% of people older than 70 years and in at least 1% of those aged over 50. The incidence of monoclonal gammopathies increases with advancing age and is higher in African-Americans than in Caucasians. Two hundred and forty-one patients from the Mayo Clinic with a monoclonal gammopathy but no evidence of MM, macroglobulinaemia, amyloidosis, lymphoma or related disorders were followed for 24-38 years. In 62 patients (26%), multiple myeloma, macroglobulinaemia, amyloidosis or a malignant lymphoproliferative disorder developed (the actuarial rate of development of serious disease at 10 years was 16%; at 20 years, 33%; and at 25 years, 40%). Thirty patients (12%) were alive and had a stable M-protein value. In 23 patients (10%), the serum M-protein level increased to 30 milligrams (3 g/dl) or more, but they did not require therapy for myeloma or related disorders. Fifty-two per cent of patients (126) died of unrelated diseases without the development of a malignant plasma cell lymphoproliferative disorder. The actual rate of development of serious disease was the same for those with IgG, IgA and IgM M-proteins. Differentiation of MGUS from myeloma or macroglobulinaemia is difficult. The M-protein value must be measured periodically and clinical evaluation carried out to determine whether or not serious disease has developed.

Multiple myeloma in the elderly

While multiple myeloma is an incurable disease for nearly all patients, current chemotherapy and supportive care can result in significant disease control and improved duration of survival and quality of life. With the average age of patients about 70, most of the high-dose curative strategies exclude the bulk of patients affected by the disease. Recent advances in understanding the biology and pathophysiology of myeloma have led to novel therapies aimed at altering drug resistance, improving duration of the plateau phase, interrupting the cytokine growth stimulation, and improving management of common complications including infections, anemia, and bone lesions. These latter approaches are not restricted to younger patients, and early evidence indicates that elderly patients are also likely to benefit.